Rationalized Volcano Plot in Heterogeneous Electrochemiluminescence

Area of Science:

• Analytical Chemistry
• Electrochemistry
• Spectroscopy

Background:

• Electrocatalysis performance relies on electrogenerated coreactant radical stability.
• Radical stability dictates the spatial extent of the electrochemiluminescence (ECL) emitting layer.
• Existing methods struggle to correlate ECL intensity with intrinsic radical stability.

Purpose of the Study:

• To establish a direct correlation between ECL intensity and intrinsic deprotonation kinetics of radical cations.
• To investigate the impact of radical cation stability on ECL emission efficiency.
• To identify an optimal stability window for efficient ECL assays.

Main Methods:

• Utilized ECL microscopy to correlate individual [Ru-(bpy)₃]²⁺-labeled bead intensity with radical cation deprotonation kinetics.
• Employed density functional theory (DFT) calculations with a hybrid cluster-continuum approach.
• Investigated model electrogenerated radical cations, including a novel aniline derivative.

Main Results:

• Disentangled intrinsic radical decomposition rates from experimental artifacts (pH, buffer effects).
• Revealed a non-monotonic, volcano-type dependence between deprotonation rate and ECL intensity.
• Identified an optimal stability window for radical cations, crucial for efficient ECL emission.

Conclusions:

• Radical cation stability is a critical parameter for optimizing ECL assay performance.
• The identified volcano-type relationship provides a new framework for designing stable radical intermediates.
• This work paves the way for rational design of improved ECL assays with enhanced sensitivity and efficiency.